Invited to use an advanced telescope at Harvard University, Étienne Léopold Trouvelot observed and painstakingly depicted a particular basin on the Moon’s surface named Mare Humorum, (or “Sea of Moisture”) with a level of specificity unobservable by the human eye. For other astrological bodies like Mars, the details eluded the telescope’s reach, so Trouvelot took artistic license in imagining the Martian surface.